This invention relates generally to a new and improved humidifying/vaporizing apparatus wherein steam is generated by electrical induction heating of water. The use of heating systems, particularly forced hot air systems, during the winter months can result in extremely low indoor humidity levels. It is well-known under such circumstances to provide humidifying/vaporizing apparatus for residential and commercial applications. The purpose of such apparatus is to increase the moisture content of the air in a defined, more or less enclosed location above the normal or ambient humidity. The enclosed location may be a single room or an entire-building.
Numerous benefits are realized by increasing humidity levels of enclosed rooms or buildings heated with forced hot air. For most people, maintaining at least a minimum humidity level in the air makes breathing easier by reducing the drying effect on the lungs and airways, reduces dust and other air-borne particulates, and creates a generally healthier and less disease-prone environment. Energy efficiencies in space heating are also realized because humid air reduces the evaporation (heat loss) from one's skin and as a result allows the reduction in the room's temperature while maintaining comfort. For adults or children with breathing difficulties, such as asthma, bronchitis or croup, sleeping may be almost impossible without a humidifier that raises the humidity of the bedroom substantially above the rest of the house. Both portable and stationary humidifying apparatus are known in the art, as are spot humifiers and those used with central heating systems.
In broad terms, humidifying apparatus can be characterized as either steam-producing or vapor-producing at below boiling point temperatures. The latter types include both water-heating models that operate below boiling point, evaporative pads (rotating or static media) and models that employ ultrasonic mist generation. Numerous contamination problems, however, have severely restricted the use of the below-boiling point humidifiers/vaporizers. Unless the water container is thoroughly cleaned and disinfected almost daily, and a clean, bacteria-free water source is used, bacteria and other infectious organisms will flourish in the warm, moist environment of the water tank and be dispersed into the air along with the water vapor. When such organisms are inhaled, they can lead to serious, even deadly, illnesses such as pneumonia and so-called Legionnaire's disease.
The danger of spreading infectious organisms can be overcome by using steam-producing humidifiers because common micro-organisms are killed by temperatures at the boiling point of water. On the other hand, the steam-producing vaporizers and humidifiers have their own restrictive drawbacks and disadvantages. First, of course, boiling point water and steam have the potential to severely scald human skin, which makes use of these humidifiers around young children especially dangerous. Second, the most common variety of steam-producing humidifier/vaporizer uses an electrical resistance element immersed in a tank of water thereby creating possible electrical shock and fire hazards.
Moreover, such apparatus is often bulky and unwieldy. Even though it may not be necessary for sanitation reasons to clean the water tank of a steam-producing humidifier/vaporizer daily, sediment, inorganic salts, and other common water contaminants will gradually settle out leaving deposits on the floor and walls of the water tank and on the heating element thereby requiring periodic cleaning or replacement of the tank and element. With conventional apparatus, this cleaning or replacement of the water tank can be somewhat difficult and time-consuming.
It is well-known in the art to heat water by the electromagnetic induction process, but this technique has not generally been applied to humidifying/vaporizing apparatus. For example, U.S. Pat. No. 1,513,087 to Buhl et al. and U.S. Pat. No. 1,425,968 to Holmes are directed to induction water heaters. U.S. Pat. No. 1,362,622 to Hendricks describes an electric induction heater for "water, gas, or other fluid." U.S. Pat. No. 2,171,080 to Ely teaches electromagnetic induction apparatus for heating air. U.S. Pat. Nos. 4,341,936 and 4,503,305 to Virgin describe electromagnetic induction systems for heating air or for heating water to produce steam for use in a heating system or to provide motive power. Each of the foregoing electromagnetic induction heating apparatuses is relatively bulky, complicated and unwieldy. For example, in the Buhl et al., Holmes, and Hendricks patents, the water to be heated must be passed from a separate source or holding tank through a system of pipes that are wrapped with electrical coils. Steam generation is not the intended objective of any of these systems, nor is it clear how these systems could be adapted to produce and transmit steam because the steam would interfere with the flow of liquid water through the pipes.
Although the apparatus of the Virgin patents is intended to produce steam from water, the heating and steam production does not occur in the water tank but rather in a separate chamber filled with magnetizable ball bearings and externally wrapped in electric induction coils. Cleaning or replacing the separate heating chamber and the hundreds of ball bearings inside would be an expensive and tedious process. Cleaning and sanitization, however, are not problems with the Virgin apparatus because the steam remains contained in a closed system and is condensed back to water vapor for recycling. The Virgin apparatus is intended for heating purposes, not for humidification. In the Virgin patents, steam and/or water vapor is not dispersed into air that will be used for breathing.
U.S. Pat. No. 4,013,742 to Lang, by contrast, is directed to humidifying and heating apparatus for respiratory gas utilizing electromagnetic induction for heating the humidifying liquid. The Lang apparatus comprises a first unit for generating electromagnetic energy and a second unit for holding and heating the humidifying fluid and adapted to be positioned in a particular configuration with respect to the first unit during operation. The second unit contains a flanged ferromagnetic plate in close proximity to the induction coils of the first unit when the two units are in operating configuration, thereby resulting in inductively heating the flanged plate and the fluid in the second unit. The apparatus of the Lang patent, however, is relatively complex, delicate, expensive to manufacture in requiring numerous precision-machined parts, and intended for very specialized applications in conjunction with hospital respirators for use with premature infants, heart surgery patients and the like. The Lang apparatus is clearly intended to humidify only a relatively small steam of respiratory gas, not an entire room or building. Moreover, the Lang apparatus is intended for use under conditions where there is continual and frequent monitoring by trained professionals. The Lang patent also recognizes the need to periodically clean the fluid-holding unit if it is to be re-used (col. 4, 11. 25-28). Although steam can be generated for sterilizing purposes using the Lang apparatus, (col. 4, 11. 35-39), it is clear that, in normal operation, it is not intended to run this apparatus at boiling point temperatures. Moreover, it is clear that Lang intends the fluid-holding unit to be cleaned and re-used because this is an expensive, precision-crafted component. The fluid-holding unit in Lang includes inlet and outlet valves, internal tubes and baffle plates, and the ferromagnetic plate all as integral components. Even assuming that the interior of Lang's fluid-holding unit could be easily accessed and the component parts removed for cleaning and re-use, such a procedure would be costly, labor-intensive and time-consuming. Clearly, then, Lang's fluid-holding unit is not intended to be disposable.
These problems with the prior art devices as well as others discussed below are overcome in whole or in part by the apparatus and method of this invention.